I believe the sensor that is located below the power steering pump is the camshaft position sensor. It really is not too difficult to replace, assuming you have the right tools, some mechanical ability, and are safe.
There are some good videos on how to do most of this job, and I will provide some pointers below. Basically to remove the power steering pump, you are going to have to remove the engine mount which means you will have to support the engine from below with a jack. Use a block of wood between the jack and the oil pan. Do not lift the car by the oil pan!! You just need to keep the engine from drooping too much when you remove the motor mount. Since you need to do this same operation to replace the serpentine belt, it might not be a bad idea to replace the belt at the same time (if the belt is looking damaged).
The following video gives a good look at how to replace the belt. This shows you how to support the engine, and remove the motor mount.
Once you have the motor mount out of the way, there are three bolts that hold the pump to the motor. To get to the bolts, you will have to rotate the power steering pulley around, to get one of the holes in the pulley to line up with the bolt heads.
Once the three bolts are out of the pump, do not try to force the pump out of its position. The first thing to do, is look at the back end of the pump, you will see where the fuel rail test port (schrader valve, similar to what you have on a tire) sticks out. The valve should have a plastic screw-on cap over it. You will drive yourself nuts trying to remove the pump if you don't first remove that cap. Of course, you don't want to damage the valve while removing the pump so just be careful. Take your time, and you can eventually rotate/slide the pump out of its location, without having to remove any of the connections to the pump itself. I've done this procedure twice on my '98 (replacing the sensor, and then much later doing the lower intake manifold gaskets). All I can say is be patient, and take a few deep breaths.
Once the pump is placed out of the way, it wouldn't hurt to use a rag to wipe the area around the sensor before you remove it. Follow the wire leads from the sensor back towards the alternator, and you should see where to disconnect the harness. Remove the sensor, being careful not to drop anything into the hole while you have the sensor removed. I think I put a little motor oil on the sensor o-ring before I put the new sensor back in.
These notes are from my memory, and since I am getting older you should also refer to a good manual. Also, if any of the other forum members see anything blatantly wrong with my content, please feel free to correct me. I guarantee I won't be offended...my wife corrects me all the time!